Wildlife populations across the globe have fallen by a staggering 58 per cent in less than 40 years, according to a Worldwide Fund for Nature report.

The Living Planet assessment, compiled by WWF with support from the Zoological Society of London (ZSL), shows that human activity and its impact on habitat loss, wildlife trade, pollution and climate change have all played a role in the drastic decline.

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And, if the trend continues, the report suggests this figure could fall even further, reaching two-thirds among vertebrates by 2020.

This chart plots the cumulative vertebrate extinctions as a percentage of all species researched

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"Science has never been clearer in telling us human activities are pushing the planet and its natural systems to the edge," said Marco Lambertini, director general of WWF.

"The Living Planet Report 2016 shows that wildlife is continuing to decline at an unprecedented rate. Since 1970 we have seen almost 60 percent decline in species populations across land, sea and freshwater and if the trend continues, global wildlife could drop by a shocking two-thirds by 2020."

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The threats facing African elephants

Almost 60% of the declining mammal populations in the report are threatened by overexploitation, namely African elephants who are also at risk from habitat loss and fragmentation.

Over the past two centuries, the report explained, there has been a drop in the range of African elephants, as well as large-scale declines predominantly caused by ivory poachers.

Elephant numbers in Selous-Mikumi in Tanzania, and its Selous Game Reserve, dropped from 44,806 in 2009 to 15,217 in 2014, a decline of 66% over a five-year period

Since 1982, the reserve has been a World Heritage Site, but in 2014 it was placed on the List of World Heritage in Danger because of widespread poaching.

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Palaeontologists characterise mass extinctions as "biological or biotic crises defined by the loss of a vast amount of species in a relatively short geological time period", explained the report.

"Such is the magnitude of our impact on the planet that the Anthropocene might be characterised by the world’s sixth mass extinction event," the report added. "In the past, such extinction events took place over hundreds of thousands to millions of years. What makes the Anthropocene so remarkable is that these changes are occurring within an extremely condensed period of time.

"Furthermore, the driving force behind the transition is exceptional. This is the first time a new geological epoch may be marked by what a single species (Homo sapiens) has consciously done to the planet – as opposed to what the planet has imposed on resident species."

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However, Stuart Pimm, professor of conservation ecology at Duke University, told the BBC some of the numbers in the report are: "very, very sketchy."

"For example, if you look at where the data comes from, not surprisingly, it is massively skewed towards western Europe. "When you go elsewhere, not only do the data become far fewer, but in practice they become much, much sketchier..."